I’ve spent a lot of time warning beginners not to jump into astrophotography right away.  Too expensive, too time-consuming, too frustrating.  And besides, beginners have their hands full just learning the sky and mastering the use of a telescope.  But is there a way to do astrophotography without the massive investment in time and expense?  Maybe not completely, but planetary imagers come close.  

The hero in this scenario comes from an unlikely source – the cheap computer webcam.  It turns out the chip inside your webcam is just fine, it’s the lousy little lens they stick in front that makes your videos look so bad.  A few years back, people began modding their webcams by unscrewing the stock lens and attaching a 1.25” nosepiece on the end.  Webcams capture video at variable rates, anywhere from around 5 fps to 60 fps.  Video is just a bunch of stills put together – at 30 frames per second, a webcam can capture 1800 images each minute.  Through the use of image stacking software like Registax, it is possible to filter out the images caught during bad seeing.  Then the software stacks the remaining good ones together to form the final image.  It sounds like black magic but it works wonderfully well.  

The Celestron NexImage

Many webcams have been used for astronomical imaging, but the model that people settled on fairly early was the $100 Philips ToUcam which uses a 640X480 Sony ICX098QB chip.  Alas, the ToUcam has been discontinued (used models have held their value extremely well on the secondary market.)  Luckily, Celestron is now selling the NexImage, a rebadged TouCam with the 1.25” nosepiece already installed.  They’ve also bundled it with some capture software and an early version of Registax (mine came with 3.0.)  If you’re one of these people scouring ebay for a ToUcam, don’t bother – just get the NexImage. 

The original Philips ToUcam (L), and with custom 1.25" nosepiece (R)

On paper, this doesn’t look promising.  The chip’s resolution is VGA, at 640 X 480.  Many are put off by this when they first hear it.  Don’t be – it’s plenty, and even some of the nicer cameras out there are still 640 X 480.  Pixel count isn’t everything!  To make matters worse, your planetary image isn’t even going to come close to filling up the space on the chip.  If you can get Jupiter 200 pixels across, you’re doing well, and Saturn and Mars are even smaller.  What’s more, the camera is a one-shot color device, so your final resolution will be even less than the 640 X 480 spec.  And finally, the NexImage is a USB 1.1 device, so on fast captures, it’s going to drop a lot of frames.  

But you know what?  None of this seems to matter in practical use.  The images people have been getting out of this $100 imager are simply stunning.  This was the image I got my first night out with a TeleVue Pronto at prime focus.  The telescope was sitting on an alt-az mount and was unguided.  

Clavius region of the moon just after first quarter

After a few more nights of playing with the device, I was able to get the following on a borrowed Orion 8” f/4 Newtonian Astrograph.  A Meade 3X barlow was used to boost image scale.  

      Jupiter and great red spot

Here’s Saturn through the Celestron C6 SCT on a CG-5 mount.  A TeleVue 2X barlow was used to boost image scale.

Jupiter through the C6 with a 3X barlow:

Ptolemaeus, Alphonsus, and Arzachel through the C8 

Plato through the C8

Some random hints and observations:  

• Visual astronomy is all about the optics and the mount.  Astrophotography, and webcam imaging in particular, is all about the mount and the focuser.  And image scale.  Interestingly, I don’t see a lot of planetary imagers bragging about the quality of their optics.  The equipment of choice seems to be a large Schmidt-Cassegrain (the Celestron C9.25 is a favorite) heavily mounted and barlowed to the hilt.  

• Be prepared for some frustration in getting the image centered on the chip.  The chip is tiny and doesn't come close to capturing the entire field of view in your eyepiece.  A rule of thumb - the image on your chip will appear as if you're using a 6 mm eyepiece.  You'll get better at this as time goes on.

• Focus, as always, is an issue.  Having a good dual-speed focuser makes life a lot easier.  Even so, it’s possible that your focuser may not have enough focus travel (in either direction) to accommodate the imager, with or without the barlow (hint: be prepared to spend money on extension tubes for your scope.)  Having a model dedicated for imaging helps.  Orion and Astro-Tech make inexpensive reflectors with nice focusers.  TeleVue, Takahashi, and other premium refractor manufacturers have scopes with focusers specially designed for imaging but these can get expensive.  

  Here's an example of an out of focus image.  I have lots of these.

  

• Before doing this at night on an actual target the first time, play with the camera, the focus travel in the telescope, and the capture settings, in the daytime.  Do this every time you work with a new scope.  There is a big difference between an 8” f/4 reflector and a 6” f/10 Schmidt-Cassegrain.  

• Get the latest version of Registax.  Version 3.0, which came with the NexImage, isn’t nearly as good as 5.1.

• When first acquiring your target in AmCap, set the shutter speed low, and the gain and brightness high.  This will exaggerate the brightness of the image to make it easier to find.

• Do everything you can to keep from using too much gain.  Too much gain results in a lot of noise.

• If you have Vista or Windows 7, the stock drivers won’t work.  This is the only page I’ve found with instructions that work.  I’ve followed these directions and have successfully installed the device on a Vista and a 7 machine.  

• No matter how bad your capture looks, try stacking it anyway.  You might be surprised at the results.  

• I've heard of people doing deep sky with these webcams, but I haven't had any luck doing this.  This is the best I've been able to do going "beyond Saturn."  It's Uranus in Jan of 2011.

  

• Start collecting barlows.  Since you're essentially imaging at prime focus, the only way to change the image scale is to use barlow lenses.  I already have a 1.8X, a 2.0X, a 2.5X, and a 3X.  Used between my C6 and C8 SCTs, that gives me 8 combinations of powers.

• Having Photoshop helps, but it’s expensive, and not strictly required.  If I need extensive Photoshopping, I usually bug one of the other members of the club.  

• When you’re not using it, keep the dust cap on the NexImage.  Many users complain about dust particles getting on the sensor.  This happened to me, and getting the little grains of dust/dirt off the chip’s clear cover was a major pain.  You'll wind up with little black dots over your images (see below.)

  

• I wish someone would publish a plain-English, layman’s guide to Registax.  I still don’t know what many of those settings and sliders do.  

• Have lots of hard drive space ready.  I have no trouble generating 10-12 Gb worth of video every hour.

I’ve been having a ball with the NexImage and have been imaging everything in sight through every telescope that comes my way.  I bought another one as a spare in case they stop selling them.  I’m also trying to rationalize upgrading to one of the cameras from The Imaging Source ($350 - $570.)  But that, as they say, is another story.  The NexImage is the most astronomical fun I’ve ever had for $100 – highly recommended!

Sidebar: From Duck to Swan - The Magic of Registax

Stacking has revolutionized planetary imaging.  You can download the latest version of Registax for free here.  If you haven't seen this before, the software really is quite amazing.  Here's a step by step process showing how the raw video is stacked to make a final image.

Step 1 - Find a suitable reference image.  This particular frame isn't very good, but you can keep manually inspecting them until you find one you like.  There are 2000 to choose from in this .avi.

Step 2 - Align the images.  This used to be a big deal, but now all you have to do is select a high contrast area, push a button, and the software does the rest.  Technically, you don't even have to be tracking, but it does help.  In this example, you can see I've set the gain a little too high (the image is a little noisy.)

Step 3 - Limit, Optimize, and Stack.  Once stacked, you can see the image is "smooth and fuzzy" which is actually good.   

Step 4 - Process wavelets.  This is a bit of a black art (I've found very few people who can agree on which sliders to move and how much) but by moving the 6 sliders to the right, you can bring out detail.  Don't do too much, as you'll increase the noise level.  Registax also contains some basic image processing features.  You can adjust color balance, gamma, brightness, contrast, RGB levels, and more.

End Sidebar